Conventionally, a vehicle seat reclining device disclosed in the patent document 1 is known. As shown in FIG. 2 of the patent document 1, the vehicle seat reclining device includes a first arm (fixed side housing 11) fixed to a vehicle seat cushion side, a second arm (rotating side housing 12) fixed to a vehicle seat back side and relatively rotatably supported by the first arm, an internal toothed portion (toothed portion provided at a ratchet 12c) disposed in an inner space (accommodating space) between the first arm and the second arm and formed on the second arm and a pawl (slide pawl 15) provided within the inner space, movably supported by the first arm and provided with an external toothed portion engaging with or disengaging from the internal toothed portion upon movement.
The vehicle seat reclining device disclosed in the patent document 1 includes a rotation cam 16 enclosed by the slide pawl 15 and arranged on the same layer with the slide pawl 15, an operating plate 18 provided between the slide pawl 15 and the rotation cam 16 and the rotation side housing 12 and an unlocking plate 19. The slide pawl 15 is provided with a cam projection 15e and cam projections 15g and 15h projecting towards the rotation side housing 12. The operating plate 18 is provided with a cam groove 18d to be engaged with the cam projection 15e and a cam groove 18d-a to be engaged with the cam projections 15g and 15h. The unlocking plate 19 is provided with a cam groove 19c to be engaged with the cam projections 15g and 15h. The length of each cam projection 15g and 15h is set to be longer than the length of the cam projection 15e. The cam projections 15g and 15h penetrate through the cam groove 18d-a. 
According to this structure of the vehicle seat reclining device, when the rotation cam 16 (operating plate 18) is rotated, slide pawls 15B to 15D are moved in a direction retracting from the ratchet 12c (engagement releasing direction) by the engagement between the cam projection 15e and the cam groove 18d. Further, when the rotation cam 16 (operating plate 18) is rotated, the slide pawl 15A is moved in a direction retracting from the ratchet 12c by the engagement between the cam projections 15g and 15h and the cam groove 18d-a and at the same the seat back is reclined toward front side and upon engagement of the cam projections 15g and 15h with the cam groove 19c, the slide pawl 15A moves to a position retracted from the ratchet 12c for fixing the position (keeping the disengagement state).
Patent Document 1: JA 2005-312891 A